Past research has demonstrated the many disadvantages faced by children who grow up apart from their fathers. Although half of all U.S. children face this situation for some period during their childhood, a father's absence from the household does not necessarily mean that he is absent from his child's life. A significant number of nonresident fathers still maintain ties with their children, although the dynamics and consequences of this relationship are not well understood. Increased attention is needed to understand the role of nonresident fathers in their children's lives and the ways in which involvement by nonresident fathers can promote child well-being. The proposed study draws on four nationally representative longitudinal data sets (the National Longitudinal Study of Adolescent Health, the National Longitudinal Study of Youth, the National Survey of Families and Households, and the Child Development Supplement to the Panel Study of Income Dynamics) and focuses on two specific aims. The first aim is to better understand how nonresident fathers participate in the lives of children and how paternal participation varies by characteristics that represent the increasing diversity of families in the U.S. We examine multiple dimensions of father involvement, and we assess differences in father involvement by race and ethnicity and father's education. We also examine the influence of mothers and stepfathers on nonresident fathers' involvement with children, and we consider how nonresident father involvement varies for children living in diverse household arrangements, including households in which the biological mother is not present. The second aim is to assess the importance of nonresident father involvement for child well-being and to determine the contexts in which such involvement is most beneficial to children. The influence of father involvement may vary with the type and extent of involvement, for different child outcomes, and at different stages of a child's life. Thus, we examine multiple dimensions of father involvement and child well-being at various points across the life course. Family contexts that may moderate the effect of father involvement include race, ethnicity, and father's education. The behavior of other important adults in the child's life, such as mothers and stepfathers, also may moderate the influence of nonresident father involvement on child well-being. We also examine whether father involvement has different effects for vulnerable and resilient children. Our findings will provide an understanding of the specific contexts that either facilitate or impede father involvement and, in turn, how father involvement shapes children's well-being and development, thereby aiding efforts to create effective policies to promote positive father-child relationships.